1. Field of the Invention
The invention refers to the association of new types of control valves for fluid circulation, applied to hydrostatic steering systems.
2. Background of the Invention
In the prior art valves include fluid circuits situated in the steering shaft, resulting in a smaller capacity of circulation of the fluid. The circuit connections do not have well-defined limits, resulting in a lesser definition of the control of the fluid circulation direction. Other difficulties are the small orifices and the strangulation which reduce the capacity of the fluid circulation between the cylinders which effect the steering direction.
In an occasional lack of fluid pressure (pump damage, fluid leak, cut of the shaft strap, engine stop) the reciprocal circulation of the fluid between the cylinders is very difficult and the fluid pressure reaches a high value, making the manual correction of the steering direction difficult. A great insecurity in the hydrostatic steering systems may derive from that situation.
The objective of the present invention is to solve the previously mentioned difficulties by obtaining a greater capacity of the fluid circulation and a higher definition of the limits of the circuits connections in the steering valves to obtain a greater facility of the manual control of the steering by means of a safety valve; and to obtain the progressive hydrostatic control of the steering by means of a progression valve.
The valves are associated and integrated inside a body C and include a first steering valve, controlling the direction of the fluid circulation in the cylinders effecting the steering; a second safety valve, controlling the direct and reciprocal circulation of the fluid between the cylinders, and a third progression valve, controlling the effects progression of the second valve.
The steering valve includes two cylinders A and B, concentric with the steering shaft D. The cylinder A rolls conjointly with the steering shaft. Channels 1, 2, 3, 4 and 5 are inserted in the contiguous peripheries of the cylinders, constituting circuits sets, each set with independent fluid circulation and whose fluid debits are gathered in collectors.
A safety valve is integrated in axial position with the steering valve and includes pistons P1 and P2 and the springs. It is connected to the steering cylinders by connections T3 and T4 with high capacity of fluid circulation. When there is a lack of the fluid pressure the spring S performs the return of the pistons, allowing the free fluid circulation between the steering cylinders and makes control of the steering easier.
The progression valve includes a cylinder and a piston PV, connected to the cylinder and the piston P2. The pistons are connected by a central shaft operating by means of the vacuum produced in the engine air admission of the vehicle, controlling the return of the piston P1 in a progressive way, from a certain speed of the vehicle.